gpio: digital pin is responsible for exporting/unexporting itself

gpiogeneric.go

@@ -2,8 +2,6 @@ package embd
 
 import (
 	"fmt"
-	"os"
-	"strconv"
 
 	"github.com/golang/glog"
 )
@@ -47,107 +45,67 @@ func (m PinMap) Lookup(k interface{}) (*PinDesc, bool) {
 	return nil, false
 }
 
+type pin interface {
+	Close() error
+}
+
 type gpioDriver struct {
-	exporter, unexporter *os.File
-
-	initialized bool
-
 	pinMap          PinMap
-	initializedPins map[int]*digitalPin
+	initializedPins map[int]pin
 }
 
 func newGPIODriver(pinMap PinMap) *gpioDriver {
 	return &gpioDriver{
 		pinMap:          pinMap,
-		initializedPins: map[int]*digitalPin{},
+		initializedPins: map[int]pin{},
 	}
 }
 
-func (io *gpioDriver) init() error {
-	if io.initialized {
-		return nil
-	}
-
-	var err error
-	if io.exporter, err = os.OpenFile("/sys/class/gpio/export", os.O_WRONLY, os.ModeExclusive); err != nil {
-		return err
-	}
-	if io.unexporter, err = os.OpenFile("/sys/class/gpio/unexport", os.O_WRONLY, os.ModeExclusive); err != nil {
-		return err
-	}
-
-	io.initialized = true
-
-	return nil
-}
-
 func (io *gpioDriver) lookupKey(key interface{}) (*PinDesc, bool) {
 	return io.pinMap.Lookup(key)
 }
 
-func (io *gpioDriver) export(n int) error {
-	_, err := io.exporter.WriteString(strconv.Itoa(n))
-	return err
-}
-
-func (io *gpioDriver) unexport(n int) error {
-	_, err := io.unexporter.WriteString(strconv.Itoa(n))
-	return err
-}
-
 func (io *gpioDriver) digitalPin(key interface{}) (*digitalPin, error) {
 	pd, found := io.lookupKey(key)
 	if !found {
-		err := fmt.Errorf("gpio: could not find pin matching %q", key)
-		return nil, err
+		return nil, fmt.Errorf("gpio: could not find pin matching %q", key)
 	}
 
 	n := pd.N
 
 	p, ok := io.initializedPins[n]
 	if ok {
-		return p, nil
+		dp, ok := p.(*digitalPin)
+		if !ok {
+			return nil, fmt.Errorf("gpio: sorry, pin %q is already initialized for a different mode", key)
+		}
+		return dp, nil
 	}
 
 	if pd.Caps&CapNormal == 0 {
-		err := fmt.Errorf("gpio: sorry, pin %q cannot be used for GPIO", key)
-		return nil, err
+		return nil, fmt.Errorf("gpio: sorry, pin %q cannot be used for digital io", key)
 	}
 
 	if pd.Caps != CapNormal {
-		glog.Infof("gpio: pin %q is not a dedicated GPIO pin. please refer to the system reference manual for more details", key)
+		glog.Infof("gpio: pin %q is not a dedicated digital io pin. please refer to the system reference manual for more details", key)
 	}
 
-	if err := io.export(n); err != nil {
-		return nil, err
-	}
+	dp := newDigitalPin(n)
+	io.initializedPins[n] = dp
 
-	p, err := newDigitalPin(n)
-	if err != nil {
-		io.unexport(n)
-		return nil, err
-	}
-
-	io.initializedPins[n] = p
-
-	return p, nil
+	return dp, nil
 }
 
 func (io *gpioDriver) DigitalPin(key interface{}) (DigitalPin, error) {
-	if err := io.init(); err != nil {
-		return nil, err
-	}
-
 	return io.digitalPin(key)
 }
 
 func (io *gpioDriver) Close() error {
-	for n := range io.initializedPins {
-		io.unexport(n)
+	for _, p := range io.initializedPins {
+		if err := p.Close(); err != nil {
+			return err
+		}
 	}
 
-	io.exporter.Close()
-	io.unexporter.Close()
-
 	return nil
 }